1. Field of the Invention
The present invention concerns the improvement of disposable inductive debit cards, such as the ones described in patent document BR 9201380-5 and BR 9304503-4 and, specifically, to the insertion of supplementary information on the cards, as well as to its reading using the existing reading devices as described in those patents.
2. Description of the Related Art
Inductive debit cards based on concepts originally contained in patents BR 7804885, DE 2650959 and U.S. Pat. No. 4,029,945 are well known and are widely used as credit elements in public telephone systems. FIG. 1 exemplifies the main features of a known card, akin to the one in FIG. 1 of above mentioned document BR 9304503-4, containing a plurality of credit elements 12, arranged in 6 rows and 9 columns, totaling 50 usable credits since four of the cells at corners 13, 14, 15 and 16 are used as indexing elements. The card also has blank strips 17 and 18, located between the central area and front end edge 19 and back edge 21, which are made use of during insertion and withdrawal of the card from the reading head.
Even though the shown card is suitable for experimental use, or small scale applications, the commercial use on a large scale basis requires the inclusion of additional information, such as, for instance, the following:
Card validation date PA1 Code of the country issuing the card PA1 Manufacturers identification code
The inclusion of this information in central area 11 would necessarily reduce the number of available credits on the card.
On the other hand, including the information on strips 17 and 18 entails, as a drawback, the need to modify the reading head, since the existing heads do not have sensors positioned at the strips. In view of the large number of telephone sets of this kind that are already in operation, such a solution would require the expenditure of large amounts of money, materials and labor, as all the installed reading heads would have to be replaced.